Method of manufacturing disk drive device for reducing adhesive amount of particles, and disk drive device manufactured by the method

ABSTRACT

In a method of manufacturing a disk drive device, a cleaning process and an assembly process are performed in succession in a clean room having a predetermined cleanness level. The cleaning process includes an alkali cleaning process, a first purified water cleaning process, a second purified water cleaning process, a spray cleaning process, a draining process and a drying process. In the first purified water cleaning process, purified water ultrasonic wave cleaning is sequentially performed on the base member of the disk drive device to be cleaned by using ultrasonic waves of frequencies of 40 kHz, 68 kHz and 132 kHz in purified water filled in a first purified water cleaning tank. The cleaned base member and other components having a predetermined cleanness level are assembled in the assembly process continuous from the cleaning process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional application based on U.S. Ser. No.12/687,103, filed on Jan. 13, 2010, which claims the benefit of priorityfrom the prior Japanese Patent Application No. 2009-092997, filed onApr. 7, 2009, the entire contents of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a disk drivedevice and a disk drive device manufactured by the method, and inparticular, to a method of manufacturing a disk drive device forreducing the adhesive amount of particles and a disk drive devicemanufactured by the method.

2. Description of the Related Art

Recently, the rotational accuracy of disk drive devices, such as HDDsand the like, has been dramatically improved by providing them with afluid dynamic bearing unit. With this improvement, a disk drive devicehas been required to have a higher density and a more increasedcapacity. For example, a disk drive device magnetically storing datarotates a recording disk with recording tracks at high speed so that aread/write operation of data is executed while the flying magnetic headof the device is tracing the recording tracks with a slight flyingheight between both of them. In order to make such a disk drive devicehave a high density and an increased capacity, the width of therecording track is required to be narrow. As the width thereof becomesmore narrow, the space between the magnetic head and the recording diskis required to be further narrowed. For example, the flying heightbetween both is required to be extremely narrow, as narrow as 10 nm orless.

For the purpose of obtaining high density, magneto-resistance effectdevices (hereinafter, referred to as MR devices) are in heavy use forthe magnetic heads. On the other hand, because an MR device is used inan extremely-narrow flying height, the occurrence of thermal asperityfailure (hereinafter, referred to as “TA failure”) or head crash failurecan become a serious problem. TA failure is caused due to momentary heatgeneration in the MR device, the heat generation triggered by kineticenergy generated by the contact of the MR device with a minute foreignsubstance on the surface of the disk while the flying magnetic headtraces the recording tracks. When the MR device is momentarily heatedfollowed by being cooled, the resistance value of the MR devicemomentarily varies such that a reproduced signal is superimposed with anoise, causing the accuracy of reading the reproduced signal to bedeteriorated. After intensive investigation, the present inventors havelearned that TA failure is caused by foreign substances, which adhere toa disk drive device by being adhered to the surface of a recording diskthrough vibration, air flow, etc., having a size of approximately 0.1 μmto several μm (hereinafter, collectively referred to as “particles”).

The disk drive device is composed of an assembly, which includes: a basemember; a bearing unit consisting of a sleeve, and a shaft relativelyrotatable with respect to the sleeve; and a hub member rotatablysupported, on the base member, by the bearing unit. The disk drivedevice is manufactured by mounting a recording disk on the hub memberand by including a magnetic head, a drive device for the magnetic head,a control circuit, and other necessary parts.

Conventionally, machine parts of which a disk drive device is composedare assembled together after being treated with a cleaning process whereforeign substances on the part such as dust are removed by cleaningwith, for example, ultrasonic waves in a cleaning tank filled with apredetermined cleaning liquid. In the cleaning process, a so-calledbatch cleaning has been the mainstream, in which the parts to be cleanedare dipped into the cleaning liquid in a state where, for example, unitsof several hundreds of the parts to be cleaned are stacked together in acleaning basket. Such a cleaning process is heavily used for cases wheresmall parts are manufactured on a large scale. In the batch cleaning,the cleaning baskets and the parts to be cleaned are dried aftercleaning and stored at a storage site such as a warehouse, as disclosedin Japanese Patent Application Publication No. Hei 7-124529. Thereafter,in an assembly process, the stored parts that have been cleaned aretaken out and fed to an assembly line where the disk drive device isassembled.

In a manufacturing method using the aforementioned batch cleaning, thelevel of the cleanness as a whole by the cleaning process is generallylow. For example, the cleanness level of a disk drive device isevaluated by the number of particles having a size greater than or equalto 0.5 μm per 1 cm2 (hereinafter, referred to as the “LPC”). The LPC isobtained in the following procedures: a device to be tested is dippedinto a tank filled with, for example, 2000 cc of purified water; anultrasonic wave of a frequency of 68 kHz and a power of 98 W areradiated onto the device to be tested for 120 seconds; and the number ofparticles existing in the purified water is counted with, for instance,a liquid particle counter such as CLS-700 or LS 200(made by ParticleMeasuring Systems, Inc., U.S.A).

In the conventional batch cleaning, there has been a large variation inthe cleanness levels of the parts to be cleaned between those that areplaced in the outer area of the cleaning basket and those in the innerarea thereof. Also, particles once detached from a part to be cleanedmay likely to adhere to another part. Further, when intending to obtaina desired cleanness level, the cleaning takes a long time, causing theworking efficiency to be deteriorated. Further, particles floating inair may sometimes adhere to a part that has been cleaned while it isbeing stored in the warehouse after the cleaning. As stated above, ifmany particles remain on the parts, TA failure is more likely to occurwhen the flying height of the magnetic head is small, becoming anobstacle for obtaining a higher density and an increased capacity of thedisk drive device. Accordingly, it can be thought that a process ofwiping the particles off with, for example, a solvent such as hexane,could be added before or after the assembly work; however, the additionof the process causes a decrease in the manufacturing efficiency, and,in many cases, the particles cannot be removed thoroughly with thewiping process.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made to solve theaforementioned problems, and a purpose of the invention is to provide atechnique in which the cleanness level of a component of a disk drivedevice can be improved and in which the possibility of the occurrence ofa TA failure can be maintained at a low level even when the flyingheight of a magnetic head is small.

In order to solve the aforementioned problems, a method of manufacturinga disk drive device according to an embodiment of the present inventionincludes at least: a base member; a bearing unit configured such that ashaft and a sleeve housing the shaft are relatively rotatable withrespect to the base member; and a hub supported by the bearing unit, inwhich at least one component of the disk drive device is cleaned whilebeing transported, in a cleaning process where a purified water cleaningusing ultrasonic waves of at least two frequencies is performed inpurified water, and in which components of the disk drive deviceincluding the one component thus cleaned are assembled in an assemblyprocess, continuous from the cleaning process, in a clean area having apredetermined cleanness level or a greater level of cleanness.

According to the embodiment, the component is subjected to an ultrasonicwave cleaning while in purified water, using ultrasonic waves of atleast two frequencies. The ultrasonic waves to be used are selected fromthe frequencies of, for example, approximately 40 KHz to 200 KHz. Inthis case, a relatively low frequency is used as a first ultrasonic wavefrequency. When a frequency is low, the wavelength is long and strongcavitation can occur, allowing for large mass particles to be removedefficiently. A relatively high frequency is used as a second frequencythereof. When a frequency is high, the wavelength is short, allowing forparticles remaining in narrow spaces to be removed efficiently by theshort wavelength. That is, large particles having a large mass, andsmall particles having a small mass and remaining in narrow spaces canbe removed efficiently by performing the ultrasonic wave cleaning usingultrasonic waves of at least two (high and low) frequencies, allowingthe cleanness level of the whole component to be enhanced. Further, theassembly work is carried out in the assembly process, continuous fromthe cleaning process, in a clean area having a predetermined cleannesslevel or a greater level of cleanness without moving the component toanother area after the cleaning, and hence the assembly of the diskdrive device can be completed in a state where the attachment ofparticles is suppressed. As a result, the probability of the occurrenceof a TA failure can be reduced even when the flying height of themagnetic heads is small.

Another embodiment of the present invention also relates to a method ofmanufacturing a disk drive device. The method is a method ofmanufacturing a disk drive device that is configured to include atleast: a base member; a bearing unit configured such that a shaft and asleeve housing the shaft are relatively rotatable with respect to thebase member; and a hub supported by the bearing unit, in which at leastone component of the disk drive device is cleaned while beingtransported, in a cleaning process where a purified water cleaning usingan ultrasonic wave is performed in purified water, and subsequently ablow cleaning, blowing a mixture of purified water and air, isperformed, and in which components of the disk drive device includingthe one component thus cleaned are assembled in an assembly process,continuous from the cleaning process, in a clean area having apredetermined cleanness level or a greater level of cleanness.

Blowing the mixture of purified water and air against the component tobe cleaned provides a great amount of kinetic energy for removingparticles. Accordingly, large mass particles remaining on the component,which cannot be removed only by the purified water cleaning, can beremoved, allowing the cleanness level of the whole component to beenhanced. Further, the assembly work is performed in the assemblyprocess in the clean area having a predetermined cleanness level or agreater level of cleanness without moving the component to another areaafter the cleaning, and hence the assembly of the disk drive device canbe completed in a state where the reattachment of particles issuppressed. As a result, the probability of the occurrence of a TAfailure can be reduced even when the flying height of the magnetic headsis small.

Yet another embodiment of the present invention relates to a disk drivedevice. The device is manufactured by either of the aforementionedmethods of manufacturing a disk drive device.

According to the embodiment, the assembly of a disk drive device can beperformed with components whose cleanness levels are enhanced by thecleaning process. As a result, the probability of the occurrence of a TAfailure can be reduced even when the flying height of the magnetic headsis small.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings which are meant to be exemplary,not limiting, and wherein like elements are numbered alike in severalFigures, in which:

FIG. 1 is a view illustrating the internal structure of a hard diskdrive device, an example of a disk drive device assembled by usingcomponents manufactured by a manufacturing method according to thepresent embodiment;

FIG. 2 is a view illustrating a state where a subassembly is made byassembling components to be cleaned in a cleaning process in themanufacturing method illustrated in the present embodiment;

FIG. 3 is a cross-sectional view taken along the cut line illustrated byM-N in FIG. 2;

FIG. 4 is a view illustrating the cleaning process and an assemblyprocess in the method of manufacturing a disk drive device according tothe present embodiment;

FIG. 5 is a graph illustrating the LPC on a disk drive devicemanufactured by a conventional manufacturing method; and

FIG. 6 is a graph illustrating the LPC on the disk drive devicemanufactured by the manufacturing method according to the presentembodiment.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described by reference to the preferredembodiments. This does not intend to limit the scope of the presentinvention, but to exemplify the invention.

Hereafter, preferred embodiments of the present invention will bedescribed based on the accompanying drawings. FIG. 1 is a viewillustrating the internal structure of a hard disk drive (HDD) 10, anexample of a disk drive device assembled by using componentsmanufactured by a manufacturing method according to the presentembodiment (hereinafter, simply referred to as a “disk drive device10”). It is noted that FIG. 1 illustrates a state where the cover of thedevice is removed to expose the internal structure.

A brushless motor 14, an arm bearing unit 16, a voice coil motor 18,etc., are mounted on the top surface of a base member 12. The brushlessmotor 14 supports, on the rotation axis thereof, a hub member 26 onwhich a recording disk 20 is mounted, allowing the recording disk 20 onwhich data can be recorded, for example, magnetically, to berotationally driven. The brushless motor 14 can be replaced by, forexample, a spindle motor. The brushless motor 14 rotationally drives therecording disk 20. The brushless motor 14 is driven by a three-phasedrive current consisting of a U-phase, a V-phase and a W-phase. The armbearing unit 16 supports, in a swing-free manner, a swing arm 22 withina movable range AB. The voice coil motor 18 makes the swing arm 22 swingin accordance with external control data. A magnetic head 24 is fixed tothe tip of the swing arm 22. When the disk drive device 10 is in anoperation state, the magnetic head 24 moves, with a swing of the swingarm 22 within the movable range AB, above the surface of the recordingdisk 20 with a slight gap between them, allowing the read/write of thedata to be performed. In FIG. 1, point A corresponds to the position ofthe outermost circumferential recording track of the recording disk 20,and point B corresponds to the position of the innermost circumferentialrecording track thereof. The swing arm 22 may be moved to a waitingposition provided in the side of the recording disk 20 when the diskdrive device 10 is in a stopped state.

In the present embodiment, a structure, which includes all of thecomponents for reading/writing data such as the recording disk 20, theswing arm 22, the magnetic head 24 and the voice coil motor 18, issometimes expressed as a disk drive device, or sometimes as an HDD. Or,only the components for rotationally driving the recording disk 20 aresometimes expressed as a disk drive device.

FIG. 2 is a view illustrating a state where a subassembly 28 is made byassembling components to be cleaned in a cleaning process in themanufacturing method illustrated in the present embodiment. In thepresent embodiment, the subassembly 28 is made by assembling, in anassembly process, the components whose cleanness levels are enhanced bya cleaning process, which will be described later, and thereafter thedisk drive device is completed by further mounting the recording disk20, the magnetic head 24, the swing arm 22, the arm bearing unit 16, thevoice coil motor 18 and the cover covering the whole of device, thecleanness levels of which are likewise enhanced.

FIG. 3 is a cross-sectional view, taken along the cut line illustratedby M-N in FIG. 2, illustrating part of the disk drive device 10. Asillustrated in FIG. 3, the disk drive device 10 according to the presentembodiment is composed of: a fixed body portion S; a rotating bodyportion R; a bearing unit 30 including a radial fluid dynamic bearingunit composed of radial dynamic pressure grooves RB1 and RB2 and alubricant agent, and a thrust fluid dynamic bearing unit composed ofthrust dynamic pressure grooves SB1 and SB2 and the lubricant agent; anda drive unit 32 rotationally driving the rotating body portion Rrelative to the fixed body portion S via these fluid dynamic bearingunits. FIG. 3 illustrates, as an example, the structure of a so-calledshaft-rotation-type disk drive device in which the hub member 26supporting the recording disk 20 and a shaft 34 rotate integrally. Somecomponents of which the disk drive device 10 is composed are included ina plurality of groups functionally divided into the fixed body portionS, the bearing unit 30, the rotating body portion R and the drive unit32. For example, the shaft 34 is included in the bearing unit 30 as wellas in the rotating body portion R.

The fixed body portion S is configured to include a base member 12, astator core 36, a coil 38, a sleeve 40, and a counter plate 42. Thestator core 36 is fixed to the outer wall surface of a cylinder portion12 a formed on the base member 12. The sleeve 40 is a cylindrical partand formed of a metal material or a conductive resin material. Thesleeve 40 is fixed to a housing hole 12 b formed by the inner wallsurface of the cylinder portion 12 a on the base member 12, with, forexample, an adhesives, etc. The disk-shaped counter plate 42 is fixed toone end of the sleeve 40, thereby sealing the inside of the base member12 in which the recording disk 20, etc., is housed.

The base member 12 can be formed by performing, for example, a cuttingprocess on a base material produced with an aluminum die cast, a pressprocess on an aluminum plate, or a press process on a steel platefollowed by nickel plating. The stator core 36 is formed by performinginsulation coating made by electro-deposition coating and powdercoating, etc., on the surface thereof after a plurality of magneticplates such as ferrosilicon plates are laminated. The stator core 36 isa ring-shaped member having a plurality of salient poles (notillustrated) protruding outwards in the radial direction, around each ofwhich the coil 38 is wound. When the disk drive device 10 is, forexample, three-phase driven, the number of the salient poles aredesigned to be nine. The wiring terminal of the coil 38 is soldered onan FPC (Flexible Printed Circuits) (not illustrated) arranged on thebottom surface of the base member 12.

The rotating body portion R is configured to include the hub member 26,the shaft 34, a flange 44 and a magnet 46. The hub member 26 is anapproximately cup-shaped member, and has an outer circumferentialcylinder portion 26 b concentric with a central hole 26 a and an outwardextension portion 26 c extending outwards at the lower end of the outercircumferential cylinder portion 26 b. The ring-shaped magnet 46 isfixed to the inner wall surface of the outward extension portion 26 c.The hub member 26 can be formed by die-molding or machining a metal suchas stainless, aluminum and iron, or a conductive resin. The magnet 46 isformed of, for example, an Nd—Fe—B (Neodymium-Ferrum-Boron) material,and on the surface thereof an anti-corrosion treatment is performed byelectro-deposition coating or spray coating, etc. In the presentembodiment, the inner circumference of the magnet 46 is magnetized with,for example, twelve poles.

One end of the shaft 34 is fixed to the central hole 26 a formed in thehub member 26, and to the other end thereof is fixed the disk-shapedflange 44. The shaft 34 can be formed of a metal having a conductivitysuch as, for example, stainless. The flange 44 can be formed of a metalmaterial or a conductive resin material. A flange-housing space 40 chousing the flange 44 is formed at one end of the sleeve 40.Accordingly, the sleeve 40 supports the shaft 34 to which the flange 44is fixed while allowing for the relative rotation between the sleeve 40and the shaft 34 in the space surrounded by a cylinder inner wallsurface 40 a and the flange-housing space 40 c.

The shaft 34 to which the flange 44 of the rotating body portion R isfixed is inserted along the cylinder inner wall surface 40 a of thesleeve 40 of the fixed body portion S. As a result, the rotating bodyportion R is rotatably supported by the fixed body portion S via theradial fluid dynamic bearing unit composed of the radial dynamicpressure grooves RB1 and RB2 and the lubricant agent, and the thrustfluid dynamic bearing unit composed of the thrust dynamic pressuregrooves SB1 and SB2 and the lubricant agent. The drive unit 32 isconfigured to include the stator core 36, the coil 38 and the magnet 46.In this case, the hub member 26 structures a magnetic circuit along withthe stator core 36 and the magnet 46. Accordingly, the rotating bodyportion R is rotationally driven by sequentially powering each coil 38in accordance with a control from a drive circuit provided externally.

The outer circumferential cylinder portion 26 b of the hub member 26according to the present embodiment is engaged with the central hole ofthe recording disk 20, and the outward extension portion 26 c positionsand supports the recording disk 20. A clamper 48 is mounted on the topsurface of the recording disk 20, and the clamper 48 is fixed to hubmember 26 by a screw 50. Thereby, the recording disk 20 is integrallyfixed to the hub member 26, allowing the disk 20 to be rotatable withthe hub member 26.

Subsequently, the bearing unit 30 will be described. The bearing unit 30is configured to include the shaft 34, the flange 44, the sleeve 40, andthe counter plate 42. The cylinder inner wall surface 40 a of the sleeve40 and the outer circumferential surface of the shaft 34, which facesthe cylinder inner wall surface 40 a, form a radial space. On at leasteither the cylinder inner wall surface 40 a of the sleeve 40 or theouter circumferential surface of the shaft 34, the radial dynamicpressure grooves RB1 and RB2 are formed, generating a dynamic pressurefor support in the radial direction. The radial dynamic pressure grooveRB1 is formed on the side remote from the hub member 26, whereas theradial dynamic pressure groove RB2 is formed on the side close to thehub member 26 than the radial dynamic pressure groove RB1. The radialdynamic pressure grooves RB1 and RB2 are, for example,herringborn-shaped or spiral-shaped grooves arranged so as to be spacedapart from each other in the axial direction of the shaft 34. The spaceformed by these radial dynamic pressure grooves RB1 and RB2 is filledwith a lubricant agent 52 such as oil. Accordingly, a high pressuresegment is generated in the lubricant agent 52 by the rotation of theshaft 34. The shaft 34 is detached from its surrounding wall surface bythe pressure, allowing the shaft 34 to be in a rotational state ofsubstantial non-contact in the radial direction.

In the present embodiment, because the hub member 26 is connected to oneend of the shaft 34, the shaft 34 receives a lateral pressure havingdifferent strengths between the side close to the hub member 26 and theside remote therefrom. Accordingly, in the present embodiment, the widthof the radial dynamic pressure groove RB1 in the axial direction of theshaft 34 is narrower than that of the radial dynamic pressure groove RB2in the same direction. Thereby, a dynamic pressure corresponding to thelateral pressure having different strengths in the axial direction ofthe shaft 34 is generated in each radial fluid dynamic bearing unit. Asstated above, a high support stiffness of the shaft 34 can be realizedby generating a high dynamic pressure, and also, an optimal balancecontributing to reduction in a rotational loss of the shaft 34 can beobtained by generating a low dynamic pressure.

As stated above, the flange 44 is fixed to the lower end of the shaft34, rotating integrally with the shaft 34. In addition, theflange-housing space 40 c in which the flange 44 is rotatably housed isformed at the central portion of the lower surface of the sleeve 40. Oneend of the flange-housing space 40 c is sealed with the counter plate 42such that the flange-housing space 40 c and a housing space of the shaft34 continuous from the flange-housing space 40 c are maintained to beair tight.

The thrust dynamic pressure groove SB1 is formed on at least either theflange 44 or the surface of the sleeve 40 facing the flange 44 in theaxial direction, whereas the thrust dynamic pressure groove SB2 on atleast either the flange 44 or the surface of the counter plate 42 facingthe flange 44. The grooves SB1 and SB2 form the thrust fluid dynamicbearing unit in cooperation with the lubricant agent 52. The thrustdynamic pressure grooves SB1 and SB2 are formed to be, for example,spiral-shaped or herringborn-shaped to generate a pump-in dynamicpressure. That is, the pump-in dynamic pressure is generated by rotatingthe flange 44 on the side of the rotating body portion R, relative tothe sleeve 40 and the counter plate 42 on the side of the fixed bodyportion S. As a result, the rotating body portion R, including theflange 44, is in a substantial state of non-contact relative to thefixed body portion S, with a predetermined space between the twoportions in the axial direction, the space created by the generateddynamic pressure, allowing the rotating body portion R, including thehub member 26, to be supported in a state of non-contact relative to thefixed body portion S.

In the present embodiment, the lubricant agent 52 filled in the gapbetween the radial fluid dynamic bearing unit and the thrust fluiddynamic bearing unit is used in common between the two bearing units. Acapillary seal portion TS in which the gap between the innercircumference of the sleeve 40 and the outer circumference of the shaft34 gradually becomes larger toward the outward of the gap, is formed onthe open end of the sleeve 40. The space, including the radial dynamicpressure grooves RB1 and RB2 and the thrust dynamic pressure grooves SB1and SB2, is filled with the lubricant agent 52, which fills up to themiddle of the capillary seal portion TS. The capillary seal portion TSprevents the lubricant agent 52 from leaking out from the fillingposition by capillarity.

A method of manufacturing the disk drive device 10, configured as statedabove, will be described based on FIG. 4. The method of manufacturingthe disk drive device 10 according to the present embodiment comprises:a cleaning process 100 in which particles that adhere to a component ofthe disk drive device 10 are removed; and an assembly process 200 inwhich components whose cleanness levels are enhanced by the cleaning areassembled into a subassembly. In the cleaning process 100 according tothe present embodiment, particles that adhere to at least either thebase member 12, the hub member 26, the sleeve 40, or the shaft 34, areremoved, as an example. The following description will be made withrespect to an example where the base member 12 is cleaned. In FIG. 4,before being cleaned, the base member 12 is inputted into an inlet port(not illustrated) by the IN side and transported to the assembly process200 through the cleaning process 100. And, an example will be describedwhere the disk drive device 10 whose assembly work is completed isdischarged from an outlet port (not illustrated) by the OUT side inassembly process 200.

In FIG. 4, the cleaning process 100 and the assembly process 200 arearranged in a clean room having two blocks separated by a simplifiedpartition 300, each clean room of which is filled with common purifiedair. A cleanness level of the clean room may be set to, for example,approximately class 1000. The clean room in the assembly process 200,the latter process, is adjusted to a positive pressure, whereas theclean room in the cleaning process 100, the former process, is adjustedto a negative pressure. By adjusting the pressure of the assemblyprocess 200 to a positive pressure, the particles that are detached froma component to be cleaned on the cleaning process 100 side, cannot enterthe assembly process 200, even when the particles are floating in air.

In the present embodiment, an example will be described where a targetof the cleaning process is, among the components of the disk drivedevice 10, the base member 12. The base member 12 is transported by atransporting apparatus 102 driven in the cleaning process 100 and atransporting apparatus 202 driven in the assembly process 200. In thecase of the present embodiment, the transporting apparatuses 102 and 202are moved clockwise in a looped manner as indicated by the solid linesin the drawing. For the transporting apparatus 102, known apparatusescan be used, the known apparatuses include: a conveyor belt; anapparatus for moving components such as the base member 12 by providinga hook for hooking the component on a loop-shaped chain; an apparatusfor moving the base member 12 by fixing a tray in which the base member12 is mounted, to a loop-shaped chain or rail; and an apparatus formoving the base member 12 on a rail. Likewise, for the transportingapparatus 202, known transporting apparatuses include a conveyor belt,an apparatus for moving the base member 12 by fixing a tray in which thebase member 12 is mounted to a loop-shaped chain or rail, an apparatusfor moving the base member 12 on a rail, etc., can be used. FIG. 4illustrates an example where a conveyor belt is adopted. The conveyorbelt is taken into consideration so as not to interfere with thecleaning by reducing a contact area with the component as much aspossible by, for example, the belt portion thereof formed into a meshshape or the transporting surface thereof provided with a plurality ofconvex portions or holes. Particles can be removed efficiently bycreating, in the conveyor belt or the tray, many holes having a diameterlarger than a quarter of the wavelength of the ultrasonic wave in thecleaning liquid such that the detergency of the ultrasonic wave isefficiently provided to the base member 12.

In the present embodiment illustrated in FIG. 4, the base member 12 iscleaned so as to have a predetermined cleanness level by removingparticles adhered thereto in the cleaning process 100, and thereafter,the shaft 34, the sleeve 40, the hub member 26, etc., whose cleannesslevels are enhanced to the predetermined level or a greater level ofcleanness, are assembled onto the base member 12 in the assembly process200. There is a possibility that inorganic particles, originating fromvarious inorganic materials, and hydrocarbon particles, originating fromvarious organic substances, may adhere to the base member 12 in acombined manner. Accordingly, in the cleaning process 100, a removalmethod suitable for each type of particles is adopted.

The base member 12 is at first inputted onto the transporting apparatus102 into the inlet port (not illustrated) at the end of the IN side andtransported toward the assembly process 200. The cleaning process 100according to the present embodiment includes an alkali cleaning process104, a first purified water cleaning process 106, a second purifiedwater cleaning process 108, a spray cleaning process 110, a drainingprocess 112 and a drying process 114.

The alkali cleaning process 104 is the first process for cleaning thebase member 12, and is performed in an alkali cleaning tank 118 filledwith alkali ion water 116. An ultrasonic generator 120 is arranged onthe bottom of the alkali cleaning tank 118. The ultrasonic generator 120performs an alkali ultrasonic wave cleaning on the base member 12 thustransported by generating, for example, an ultrasonic wave of afrequency of 40 kHz.

As stated above, there is a possibility that inorganic particles,originating from various inorganic materials, and hydrocarbon particles,originating from various organic substances, may adhere to the basemember 12 in a combined manner. Because the hydrocarbon particles have alow affinity to purified water, the efficiency of removing thehydrocarbon particles by the cleaning using purified water is low.Although a method of removing the hydrocarbon particles by using asurface acting agent can be considered, any remaining components of theresidue of the surface acting agent, if any, may possibly vaporize andcontaminate the recording disk. Further, multi-stage rinsing processesare needed to reduce the residue of the surface acting agent, possiblycausing the apparatus to be large in size. Accordingly, in the presentembodiment, the hydrocarbon particles are at first removed in the alkalicleaning process.

Having many negative ions obtained by, for example, the electrolysis ofpurified water added with an electrolyte, the alkali ion water 116reacts well with the hydrocarbon particles, and exerts a good capabilityfor removing the particles by emulsification and dispersion. Further,having a low surface tension, the alkali ion water 116 infiltrates theinside of narrow spaces such as holes formed in the base member 12,allowing particles to be removed effectively.

The operation of an ultrasonic wave can be improved by performing theprocess of removing dissolved air in the alkali ion water 116 by, forexample, reducing an amount of the dissolved air to 5% or less.Regarding this case, when one intends to reduce the amount of thedissolved air to less than 2%, the apparatus for the process is large insize, and therefore it is preferable that the amount thereof is withinthe range of 2 to 5% in terms of obtaining a low-cost and an efficientalkali ultrasonic wave cleaning. Although a necessary effect of removingparticles can be expected with alkali ion water having a pH of 10 ormore, water having a pH of 11 to 13 is used in the present embodiment.It is because the present inventors have obtained an experimental resultthat, with respect to the probability of the occurrence of a TA failurein the disk drive device 10, the necessary level can be secured byperforming the alkali ultrasonic wave cleaning using the alkali ionwater 116, having a pH of 11 to 13, and having the amount of dissolvedair be 2 to 5%, and further by performing the subsequent purified watercleaning.

If many ions remain on the disk drive device 10, the insulationproperties of the high impedance portions may be deteriorated. In thepresent embodiment, because the purified water cleaning is performedfollowing the alkali ultrasonic wave cleaning, the problems due to theremaining ions and the problem of contamination due to vaporization ofthe remaining element, etc., can be avoided.

In the present embodiment, a pump 122 for pumping the alkali ion water116 is provided at the end L on the IN side of the alkali cleaning tank118. The alkali ion water 116 pumped by the pump 122 is discharged froma discharge nozzle 124 provided at the end R on the OUT side of thealkali cleaning tank 118 after the foreign substances floating in thewater 116 are captured with a filter (not illustrated). By performingthis purification process, a current of water, flowing from the OUT sideto the IN side, is generated in the alkali cleaning tank 118, in theopposite direction that the base member 12 is transported. In FIG. 4,the water current flowing in the opposite direction is indicated bydashed lines. Accordingly, the particles, once removed from the basemember 12, float away from the vicinity of the base member 12 in thewater current that flows in the opposite direction and are captured withthe filter. As a result, the possibility of reattachment of theparticles during the alkali ultrasonic wave cleaning can be reduced.Further, an efficient process of removing the particles can be performedwith the use of a cleaning liquid that always has a high cleanness leveldue to the purification process.

The base member 12 treated in the alkali cleaning process 104 istransported to a first purified water cleaning process 106. Not only thebase member 12 but also other components of the disk drive device 10have complicated shapes in which narrowly spaced portions, such asholes, and broad, flat portions are combined. In the case of theultrasonic wave cleaning, an ultrasonic wave of a relatively lowfrequency has a long wavelength and a large cavitation effect, and henceis suitable for removing large mass particles or firmly adheredparticles. On the other hand, an ultra sonic wave of a relatively highfrequency has a short wavelength and is hence suitable for removingparticles in a narrow space. Accordingly, in the present embodiment, thepurified water ultrasonic wave cleaning is performed by using ultrasonicwaves of at least two or more of frequencies. Alternatively, a purifiedwater cleaning using an ultrasonic wave of one frequency in purifiedwater may be performed following the alkali cleaning.

In the first purified water cleaning process 106, a first purified watercleaning tank 126 is filled with purified water 128. An ultrasonicgenerator 130 generating an ultrasonic wave of a frequency of 40 kHz, anultrasonic generator 132 generating an ultrasonic wave of a frequency of68 kHz, and an ultrasonic generator 134 generating an ultrasonic wave ofa frequency of 132 kHz are arranged on the bottom of the first purifiedwater cleaning tank 126. Each of the ultrasonic generators 130,132, and134 performs the purified water ultrasonic wave cleaning on the basemember 12 thus transported. As a result, the large mass particlesadhered to the base member 12 and the small particles that are adheredin to a narrow space can be efficiently removed. By irradiating the basemember 12 with ultrasonic waves of different frequencies in the samefirst purified water cleaning tank 126 at a time in order to perform anultrasonic wave cleaning on the member 12, a vibration that is a beat ofthese ultrasonic waves is generated. As a result, cleaningnon-uniformity can be reduced and the capability of removing theparticles can be improved. Further, the efficiency of space can beimproved and the apparatus cost can be reduced in comparison with thecase where the cleaning tanks are separated for each frequency.

As stated above, the present inventors have obtained an experimentalresult that, with respect to the probability of the occurrence of a TAfailure in the disk drive device 10, by performing multi-stage purifiedwater ultrasonic wave cleaning in which an ultrasonic wave of a higherfrequency is used toward the end of the cleaning, such as a frequency of40 kHz at the start of the cleaning following the alkali ultrasonic wavecleaning, subsequently an intermediate frequency of 68 kHz, and finallya further higher frequency of 132 kHz at the end of the cleaning, therequisite level can be secured. The inventors also have obtained anexperimental result that, in the case of using the ultrasonic waves inmulti-stages, various particles having different sizes and masses can beefficiently removed by setting the frequency of the ultrasonic wave usedin the subsequent stage to a value obtained by multiplying the frequencythereof used in the preceding stage by approximately 1.5 to 2. If anultrasonic wave of a frequency of 40 kHz or less is used, the cavitationeffect becomes too strong, causing the aluminum of which the base member12 is formed to be possibly corroded or eroded; therefore, it ispreferable that such a frequency is not used.

Also in the first purified water cleaning tank 126, a pump 136 forpumping purified water 128 is provided at the end L on the IN side ofthe tank 126. The purified water 128 pumped by the pump 136 isdischarged from a discharge nozzle 138 provided at the end R on the OUTside of the first purified water cleaning tank 126 after the particlesfloating in the water 128 are captured with a filter (not illustrated).With the purification process, a current of water indicated by thedashed arrow, flowing from the OUT side to the IN side, is generated inthe first purified water cleaning tank 126 in the opposite directionthat the base member 12 is transported. Accordingly, the particles, onceremoved from the base member 12, float away from the vicinity of thebase member 12 by the water current and are captured with the filter. Asa result, the possibility of reattachment of the particles during thepurified water ultrasonic wave cleaning can be reduced.

The base member 12 treated in the first purified water cleaning process106 is transported to a second purified water cleaning process 108. Thesecond purified water cleaning tank 140 is also filled with the purifiedwater 128. A jet cleaning nozzle 142, which generates a jet flow suchthat a current of water generated by the jet flow cleans the base member12 to remove particles remaining thereon, is arranged on the bottom ofthe second purified water cleaning tank 140. By continuously providingan acting force to the surface of the base member 12 with such a strongwater current generated, the particles, such as the particles notremoved by the ultrasonic wave cleaning in the first purified watercleaning process 106 and that have reattached to the base member 12while being transported in the first purified water cleaning tank 126,can be redetached therefrom in the second purified water cleaning tank140. Pumps 144 for pumping the purified water 128 are provided at theend L on the IN side and at the end R on the OUT side of the secondpurified water cleaning tank 140. The purified water 128 pumped by thesepumps 144 is discharged from a jet cleaning nozzle 142 after foreignsubstances such as the particles floating in the water 128 are capturedwith a filter (not illustrated). With the purification process, watercurrents indicated by the dashed arrows, flowing from the center to theIN side and OUT side, are generated in the second purified watercleaning tank 140. As a result, the particle detached from the basemember 12 by the jet flow float away from the direction of the basemember 12 by floating in the water currents generated by thepurification process. Accordingly, the possibility of reattachment ofthe particles, once removed from the base member 12, can be reduced.Further, the jet flow from the jet cleaning nozzle 142 becomes the cleanpurified water 128 from which the particles are removed, allowing thecleanness efficiency to be improved.

When performing the ultrasonic wave cleaning in the alkali cleaningprocess 104, the first purified water cleaning process 106 or the secondpurified water cleaning process 108, etc., if the base member 12 istransported, in the cleaning liquid, in a state where the surfacethereof having a large area is kept horizontal, there is a possibilitythat an air bubble caused by the cavitation may be sucked in and held inthe irregular sections of the base member 12. Because an ultrasonic wavedoes not act on the portion where the air bubble is held, the particleson the portion are difficult to be removed. Accordingly, in the presentembodiment, a surface having a small area of the base member 12 is to bepositioned ahead and dipped into the cleaning liquid, thereby allowingan air bubble thus held to be released from the base member 12. Forexample, in FIG. 4, the base member 12 is dipped into the cleaningliquid at a slant in which the surface having a small area of the member12, i.e., the edge surface thereof, is positioned ahead. The angle canbe, for example, 70°. As a result, the occurrence of a phenomenon wherean air bubble is sucked in and held in the base member 12 is reduced,thereby allowing the ultrasonic wave cleaning to be successfullyperformed during the moving of the cleaning liquid.

In the present embodiment, the cleaning tanks are structured into amulti-stage structure provided with the alkali cleaning tank 118, thefirst purified water cleaning tank 126 and the second purified watercleaning tank 140, and the base member 12 is at a slant when dipped intoand discharged from each cleaning tank. As a result, an air bubblesucked in and held in the base member 12 can be removed efficiently. Bysetting the angle at which a component to be cleaned such as the basemember 12 is dipped into and discharged from the tank, to an anglewithin the range of 20° to 90°, it becomes more difficult for airbubbles to be sucked in and becomes easier for air bubbles sucked in tobe released; however, it is more preferable that the angle is, forexample, within the range of 45° to 80° in order to obtain a stableeffect. Further, as stated above, because the water current moving inthe opposite direction in which the base member 12 is transported, isformed in the cleaning liquid in each cleaning tank, the effect ofaccelerating the release and removal of the air bubble sucked in andheld, can also be obtained by this water current. As another embodiment,the base member 12 transported in the cleaning liquid may be rotated orshaken. By being transported while being rotated, the whole base member12 can be uniformly subjected to the ultrasonic wave cleaning, and therelease of the air bubble sucked in and held can be performedefficiently. The same effect can be obtained when shaking the basemember 12.

In the present embodiment, an ultrasonic generator generating ultrasonicwaves is arranged on the bottom of each cleaning tank. As a result ofrepeated experiments, the present inventors have obtained a result that,comparing the case where the base member 12 is transported through thearea close to the bottom of the liquid with the case where the basemember 12 is transported through the area close to the surface thereof,the effect of removing the particles is lower in the former case.Therefore, in the present embodiment, the efficient removal of theparticles can be realized by transporting the base member 12 through thearea closer to the surface of the liquid than half the depth thereof inthe cleaning tank. Specifically, when the depth of the liquid from thesurface to the bottom in each cleaning tank is 24 cm, the base member 12is transported through the area closer to the surface of the liquid thanthe depth of 12 cm, and thereby an efficient removal of the particleshas been found. Further, by transporting the base member 12 through thearea closer to the surface thereof than the depth of 8 cm, a result hasbeen obtained that the effect of removing the particles is greaterimproved. Moreover, by transporting the base member 12 through the areacloser to the surface thereof than the depth of 6 cm, the effect ofremoving the particles has been far more improved. Even when anultrasonic generator generating ultrasonic waves is arranged, forexample, on the side surface of the cleaning tank other than the bottomthereof, the same effect can be obtained by transporting the base member12 through the same area.

The present inventors have obtained an experimental result that, whenthe interval between the base members 12 transported in succession isnarrow in the purified water cleaning process, an ultrasonic wave doesnot act sufficiently on the portion facing the narrow space, and theparticles once removed are difficult to be discharged from the vicinityof the base member 12. From repeated experiments, the inventors havefound that the aforementioned problem can be avoided by setting theinterval between the base members 12 to a value larger than a quarter ofthe wavelength of the ultrasonic wave thus used in the water in thepurified water cleaning process. For example, when using an ultrasonicwave of a frequency of 68 kHz during the condition in which the acousticvelocity in water is 1500 msec, the wavelength of the ultrasonic wave isapproximately 22 mm, and hence the interval of the base members 12 hasbeen set to 5.5 mm or more. As a result, the sufficient removal of theparticles can be found even on the portions facing the narrow spacebetween respective base members 12, and the further reattachment of theparticles has been suppressed. The inventors also have obtained anexperimental result that, by setting the interval between the basemembers 12 to a value larger than half the wavelength of the ultrasonicwave in water, a more efficient ultrasonic wave cleaning can berealized, and the particles once removed can be easily discharged fromthe vicinity of the base member 12.

In the process drawing in FIG. 4, the base member 12 treated in thesecond purified water cleaning tank 140 is transported to the spraycleaning process 110. Of the metal particles adhered to the base member12, the particles having a relatively large size has a large mass, andhence such particles are sometimes not removed only by the ultrasonicwave cleaning and the jet cleaning performed in the liquid. Accordingly,the spray cleaning process 110 is arranged in the clean room continuousfrom the alkali cleaning process 104, the first purified water cleaningprocess 106 and the second purified water cleaning process 108. In thespray cleaning process 110, a blow cleaning is performed by blowing amixture 148 of purified water and air from spray nozzles 146 arrangedaround the base member 12. Mixing purified water with air to make fineparticles of purified water and spraying the mixture at a high velocitycan provide high kinetic energy. In this case, because the kineticenergy of a purified water particle is proportional to the productobtained by multiplying the mass of the purified water particle by thesquare of the velocity, the kinetic energy can be adjusted bycontrolling the diameter of the purified water particle and the blowingvelocity, i.e., the degree of compaction of air. In the presentembodiment, the inventors have obtained an experimental result that, byperforming the spray cleaning process 110 in which the diameter of thepurified water particle is within the range of 20 to 80 μm and theblowing velocity is within the range of 20 to 80 m/s, following thealkali cleaning process 104, the first purified water cleaning process106 and the second purified water cleaning process 108, a required levelwith respect to the probability of the occurrence of a TA failure in thedisk drive device 10 can be secured. When forming a suction port in thedirection in which the mixture 148 jetted from the spray nozzle 146 isexpected to spatter after colliding with the base member 12, theparticle detached and removed from the member 12 by the mixture 148 canbe recovered along with the mixture 148. As a result, the floating ofthe particles and reattachment thereof can be both avoided. Therecovered mixture 148 is made pass through a filter (not illustrated)such that the purified water thereof is cleaned, and is sent to thespray nozzle 146 again.

As stated above, by performing the spray cleaning in the clean roomcontinuous from the previous process without storing the components inordinary air after being subjected to the purified water cleaning, theadhesion of particles floating in the air to the base member 12 can beeasily avoided. As a result, the adhesion of the particle between theprocesses can be greatly improved. Likewise, the adhesion of theparticles floating in air to the base member 12 can be easily avoided byperforming the subsequent process in a continuous clean room, withoutstoring the components in ordinary air between the alkali cleaningprocess 104 and the first purified water cleaning process 106, the firstpurified water cleaning process 106 and the second purified watercleaning process 108, the spray cleaning process 110 and the drainingprocess 112, and the draining process 112, and the drying process 114,etc., the last two described later.

In most of the conventional cleaning processes using liquids, componentssuch as the base member are dipped into a cleaning tank in a state whereunits of several hundreds of the components are stacked together in abasket, etc., so that an ultrasonic wave acts on the components thathave been left to rest in the cleaning tank for a certain time. In thiscase, the rate of removal of the particles is extremely decreased in theportions where the components are overlapped together. The same is truewith the components placed in the central area of the basket. Further,because areas in which an ultrasonic wave acts strongly and areas inwhich an ultrasonic wave acts weakly are generated in the cleaning tank,the rate of removal of the particles is decreased with a componentdipped into an area in which an ultrasonic wave acts weakly, causing alarge non-uniformity of removing the particles to be created due to thedifference between the ultrasonic wave actions for every component.Accordingly, the total cleaning time is required to be long, causing theworking efficiency to be deteriorated. Further, the particles onceremoved continue to float near the components due to the congestion ofmany components, sometimes causing the reattachment of the particlesonto the components.

Contrary to this, in the cleaning method according to the presentembodiment, the base member 12 is arranged on the transporting apparatus102 so as to create an interval with another base member 12 in thepurified water process, as stated above. And, the ultrasonic waves acton the member 12 while transporting the member 12 in a fixed direction.And, because each base member 12 passes through the same ultrasonic wavearea, a difference between the ultrasonic wave actions for each basemember 12 hardly exists, allowing the non-uniformity of removing theparticles to be suppressed. Also, because the base member 12 mounted onthe transporting apparatus 102 is transported at a fixed speed,particles once removed easily float away from the vicinity of the basemember 12, allowing the possibility of reattachment to be reduced.Specifically, the transporting apparatus 102 is configured such that thebase member 12 is transported at a speed of, for example, 3 cm/s. Withrespect to the speed, the inventors have obtained an experimental resultthat, a speed of 0.5 cm/s or less is not preferred because it makes theworking time too long; and a speed of 20 cm/s or more is not preferredbecause it makes the working time too short, likely causing thenon-uniformity of removing the particles. Accordingly, the inventorshave found the result that the particles can be successfully removed bysetting the moving speed of the transporting apparatus 102 to a valuewithin the range of 0.5 cm/s to 20 cm/s.

The base member 12 treated in the spray cleaning process 110 istransported to the draining process 112. In the draining process 112,water is drained by blowing clean air 152 against the base member 12from an air nozzle 150. A cleanness level of the clean air in this caseis preferably class 100 or less. The base member 12 may also be rotatedor shaken in the draining process 112, allowing further efficientdraining to be performed.

The base member 12 treated in the draining process 112 is transported tothe drying process 114. In the drying process 114, the whole base member12 is dried by hot air and a far-infrared heater 154. The base member 12may also be rotated or shaken in the drying process 114, allowingfurther efficient drying to be performed.

The base member 12 treated in the drying process 114 is transported tothe assembly process 200. In the present embodiment, the starting end ofthe transporting apparatus 202 in the assembly process 200 is installedso as to enter the cleaning process 100 side such that the base member12 is delivered from the transporting apparatus 102 to the transportingapparatus 202 by a load changing apparatus (not illustrated) arrangedbetween the two transporting apparatuses 102 and 202.

In the assembly process 200, with the base member 12 whose cleannesslevel is enhanced to a predetermined value by the cleaning process, areassembled the sleeve 40, the shaft 34 and the hub member 26, thecleanness levels of which are also maintained at a predetermined valueor a greater value. As stated above, because the cleaning process 100and the assembly process 200 are arranged in the continuous clean room,the reattachment of the particles to the disk drive device 10 underassembly can be greatly reduced. Thereafter, the recording disk 20 whosecleanness level is enhanced is further mounted on the hub member 26, andthe magnetic head 24, the swing arm 22, the arm bearing unit 16, thevoice coil motor 18, the control circuit, and other necessary componentsare mounted, completing the assembly of the disk drive device 10. Theassembly work may be performed in the assembly process 200 or in anotherclean room having a predetermined cleanness level.

In the aforementioned embodiments, an example in which the base member12 is cleaned in the cleaning process 100 has been described. However,the same cleaning can also be performed on the sleeve 40, the shaft 34and the hub member 26, etc., that are components of the disk drivedevice 10, in the cleaning process 100, allowing for the same effect tobe obtained. Further, in the aforementioned embodiments, an example inwhich the base member 12 is transported as a single body through thecleaning process. However, the base member 12, the sleeve 40, the shaft34, the hub member 26 and the like of which the disk drive device 10 iscomposed, may be mounted, as one group, on a common conveyance paletteto be transported, so that these components are subjected to thecleaning and drying processes. In this case, it is preferable that thecomponents included in the one group are arranged on the commonconveyance palette such that the interval between two adjoiningcomponents is maintained at the aforementioned level at which theultrasonic wave cleaning is successfully performed, as stated above. Bytransporting and cleaning one set of components on the common conveyancepalette, the cleanness of the components of the disk drive device 10 arethe same levels as each other, contributing to quality stability.Further, as is sometimes the case, each component exhibits a biasedfeature according to the manufacturing lot or processing time, even ifthe processing accuracy is within the acceptable range. In such a case,the components compatible with each other, combined with each other inadvance, can be mounted on the common conveyance palette. As a result,the assembly work can be smoothly performed by combining the componentsthat are compatible with each in the assembly process 200, contributingto quality stability.

As stated above, by performing the cleaning process 100 in which eachcleaning process and the assembly process 200 are conducted incontinuous clean rooms, the number of particles that are adhered to thedisk drive device 10 can be greatly reduced, and the variation in thenumbers of adhered particles can be reduced. As a result, theprobability of the occurrence of a TA failure in the disk drive device10 can be small even when the flying height of the magnetic head 24 issmall, allowing an easy accurate reading of a reproduced signal in theassembled disk drive device 10.

FIG. 5 represents the LPC indicating the number of the particles havinga size greater than or equal to 0.5 μm per 1 cm2 on a disk drive devicein which a sleeve and a hub member are mounted on a base membermanufactured by a conventional batch-type manufacturing method. Thecleanness levels LPCs on five disk drive devices to be tested vary inthe range of 5000 to 10000 particles, and it can be understood that itis difficult to maintain the LPC to be stable at 8000 particles or less.Contrary to this, FIG. 6 represents the LPCs on the disk drive device 10in which the sleeve 40, the shaft 34 and the hub member 26 are mountedon the base member 12 manufactured by the manufacturing method accordingto the present embodiment illustrated in FIG. 4. In this case, thefollowing result has been obtained: the LPCs indicating the numbers ofthe particles having a size greater than or equal to 0.5 μm per 1 cm2 onthree disk drive devices to be tested are reduced to approximately 2000particles or less; and a variation in the LPCs is small.

As stated above, in the disk drive device having the LPC of 5000 to10000 particles obtained by a conventional manufacturing method, thereis a large variation in the numbers of the particles for every device.Accordingly, the number of particles needs to be checked in aninspection process of the disk drive device, so that a device having alarge number of particles will be prevented from being shipped as is. Inthis case, a particular process of removing the particles, for example,wiping the particles off, etc., is added, and hence the efforts formanufacturing the device have been increased. Further, in this case, arotational speed of the recording disk is sometimes lowered in order toreduce the possibility of the occurrence of a TA failure, causing thereading of data to be slow. Contrary to this, the LPC can be reduced to2000 particles or less on the disk drive device 10 provided with thesleeve 40, the shaft 34 and the hub member 26 on the base member 12, byusing the manufacturing method according to the present embodiment. Thatis, the variation in the number of particles for every device can besmall. As a result, a particular process of removing the particles isnot necessary, allowing the efforts of manufacturing the device to bereduced. Further, the rotational speed of the recording disk does notneed to be lessened, allowing a high-performance disk drive device 10 tobe provided.

In the aforementioned method of manufacturing the disk drive device 10,the LPC on the disk drive device 10 can be reduced to 1500 particles orless by extending the cleaning time with the speed at which thecomponent to be cleaned such as the base member 12 is transported beingadjusted. With the same way, the LPC on the disk drive device 10 can bereduced to 1000 particles or less. Such control of the LPC is preferablyperformed such that, comparing the effort and work efficiency necessaryfor the control thereof with those which are necessary for removing theparticles, the efficiency is improved.

In the aforementioned embodiment, the descriptions have been made,taking a shaft-rotation-type disk drive device 10 as an example of thedisk drive device 10. However, the manufacturing method according to theembodiment can be applied to a disk drive device having other structuressuch as a shaft-fixed-type disk drive device, and in that case, the sameeffect as the present embodiment can be obtained.

The present invention shall not be limited to the aforementionedembodiments, and various modifications, such as design modifications,can be made with respect to the above embodiments based on the knowledgeof those skilled in the art. The structure illustrated in each drawingis intended to exemplify an example, and the structure can beappropriately modified to a structure having a similar function, whichcan provide similar effects.

What is claimed is:
 1. A method of manufacturing a disk drive devicecomprising a base member, a bearing unit, a hub supported by the bearingunit so that the hub can rotate with respect to the base member, themethod including a step of cleaning at least one component of the diskdrive device, wherein the step of cleaning includes the steps of:subjecting said at least one component to an ultrasonic wave whiletransporting said at least one component in purified water; and sprayinga mixture of liquid and air on said at least one component, the methodfurther includes a step of assembling the disk drive device includingsaid at least one component in a clean area which is continuouslyconnected with an area in which the step of cleaning is performed, theclean area having a predetermined level of cleanliness or higher levelof cleanliness.
 2. The method according to claim 1, wherein, in the stepof spraying, the mixture of air and purified water particles with thediameter ranging from 20 micrometers to 80 micrometers is sprayed with avelocity ranging from 20 m/s to 80 m/s.
 3. The method according to claim1, wherein, in the step of spraying, a suction port for recovering themixture is provided at a position toward which at least a part of themixture is directed after the mixture has collided with said at leastone component.
 4. The method according to claim 1, wherein the step ofcleaning includes an alkali cleaning in which said at least onecomponent of the disk drive device is subjected to an ultrasonic wave inalkali ion water while being transported, prior to the step ofsubjecting.
 5. The method according to claim 1, wherein the clean areain the step of assembling has a positive pressure relative to the cleanarea in the step of cleaning.
 6. The method according to claim 1,wherein, in the step of subjecting, said at least one component issubjected to ultrasonic waves with two different frequencies.
 7. Themethod according to claim 6, wherein, in the step of subjecting, anultrasonic wave used on the cleaning end side has a frequency higherthan that of an ultrasonic wave used on the cleaning start side.
 8. Themethod according to claim 1, wherein the step of subjecting includes astep of hitting said at least one component with a jet flow of purifiedwater.
 9. The method according to claim 1, wherein, in the step ofcleaning, said at least one component of the disk drive device istransported while being provided with either a rotational movement orvibrational movement, or both, at least in a cleaning liquid.
 10. Themethod according to claim 1, wherein the step of cleaning includes astep of spraying clean air on said at least one component after it haspassed the step of spraying the mixture.
 11. The method according toclaim 1, wherein the step of cleaning includes a step of drying said atleast one component, after it has passed the step of spraying themixture, by hot air and a far-infrared heater.
 12. A method ofmanufacturing a disk drive device comprising a base member, a bearingunit, a hub supported by the bearing unit so that the hub can rotatewith respect to the base member, the method including the steps of:subjecting at least one component of the disk drive device to anultrasonic wave while transporting said at least one component inpurified water; spraying a mixture of liquid and air on said at leastone component; and assembling the disk drive device including said atleast one component in a clean area having a predetermined level ofcleanliness or higher level of cleanliness.
 13. The method according toclaim 12, wherein, in the step of spraying, the mixture of the air andpurified water particles with the diameter ranging from 20 micrometersto 80 micrometers is sprayed with a velocity ranging from 20 m/s to 80m/s.
 14. The method according to claim 12, wherein, in the step ofspraying, a suction port for recovering the mixture is provided at aposition toward which at least a part of the mixture is directed afterthe mixture has collided with said at least one component.
 15. Themethod according to claim 12, further including a step of alkalicleaning in which said at least one component of the disk drive deviceis subjected to an ultrasonic wave in alkali ion water while beingtransported, prior to the step of subjecting.
 16. The method accordingto claim 12, wherein, in the step of subjecting, said at least onecomponent is subjected to ultrasonic waves with two differentfrequencies.
 17. The method according to claim 12, further including astep of spraying clean air on said at least one component after it haspassed the step of spraying the mixture.
 18. A method of manufacturing adisk drive device comprising a base member, a bearing unit, a hubsupported by the bearing unit so that the hub can rotate with respect tothe base member, the method including the steps of: spraying a mixtureof liquid and air on at least one component of the disk drive device;and assembling the disk drive device including said at least onecomponent in a clean area having a predetermined level of cleanliness orhigher level of cleanliness.
 19. The method according to claim 18,wherein, in the step of spraying, the mixture of the air and purifiedwater particles with the diameter ranging from 20 micrometers to 80micrometers is sprayed with a velocity ranging from 20 m/s to 80 m/s.20. The method according to claim 18, wherein, in the step of spraying,a suction port for recovering the mixture is provided at a positiontoward which at least a part of the mixture is directed after themixture has collided with said at least one component.